Japanese Patent Application Laid-Open No. 2001-108465 discloses a guiding route searching system. The guiding route searching system sets a destination by adjusting a coordinate position and a scaling magnifier and the like so that the destination is displayed on a map. Then, the presence of the route image from the current, position to the destination is checked and, if it is present, the route image is input. The criteria are to select the road nearby the traced route image as a candidate so that the passage cost for roads nearby the route image is reduced. The roads nearby the route image are combined together and the combination with the lowest cost from the current position to the destination is searched as the guiding route.
As Japanese Patent Application Laid-Open No. 2001-108465 discloses, some devices for searching a guiding route can specify a route, which a user wants to pass through on a map. If a predetermined route is specified on a touch panel when a check screen that displays a destination and the like appears, a desired route can be specified.
In the case of Japanese Patent Application Laid-Open No. 2001-108465, however, after a desired route is specified, a passage cost for the roads nearby the route image is lowered and the route is searched. When the route from the current position to the destination is searched after the route image is specified as such and if the specified desired route is at a distant from a route which is searched by a device for searching a guiding route with no specification of such a passing route, a route that does not pass through a user-specified route may be generated as a guiding route. For example, a route that passes between the user-specified route and the guiding route that is generated when a passing route is not specified may be generated as a guiding route. If such a guiding route is generated, it is impossible to guide a user to the destination through a route, which the user wants to pass through.
Then, it can be considered to generate routes from the current position to the destination and then let a user to specify a route that the user wants to pass through on a screen for checking the generated routes. In such a case, a guiding route that takes a user-specified route can be generated as a partial section of the generated guiding routes is replaced for a user-specified pass-through road. The user can be guided to the destination through a guiding route that the user wants to pass through.
If a partial guiding route is generated and then replaced for a user-specified pass-through route, however, the replaced guiding route becomes inappropriate as a guiding route from the current position to the destination.
Some roads are available for traffic in both directions, the others are available for traffic in only one direction. A user moves his or her finger along the road displayed on the check screen for a guiding route to specify the passing route. Sometimes, the user-specified road as a passing route on the check screen for a guiding route may unavailable for traffic according to the passing direction for the guiding route from the current position to the destination.
Some roads are prohibited for right turn. A user moves his or her finger along the road displayed on the check screen for a guiding route. Sometimes, the user-specified road as a passing route on the check screen for a guiding route may unavailable for traffic according to the passing direction for the guiding route from the current position to the destination.
If a part of the guiding route is generated and then replaced for another one based on passage specification by a user, the user needs to specify a road that he or she wants to pass through to cross the generated guiding route in specifying the road. There is also a problem in that the user needs to specify the route including the specifying road to cross the guiding route also for the roads other than the road that the user wants to pass through.